In the manufacturing of vehicles, the aspect of lightweight design has led to increasing use of hybrid constructions for the vehicle body. Typical variants in this regard are components of the outer skin of the vehicle body which are made of a light-weighted metallic material (for example, an aluminum alloy), optionally with reinforcement members of steel material, and which are arranged on steel frame constructions. Alternatively, as described, for example, in DE 198 24 932 A1, the outer skin component can consist of sheet metal while the reinforcement member is made of a light metal alloy. Further, the frame construction (such as the space frame) can be realized in mixed construction. DE 10 2004 004 386 describes examples of mixed construction of covering parts for use as components of the vehicle body.
For lightweight design, use is made of lightweight metallic materials, for example, Al alloys, which have distinctly lower corrosion rates than steels. In this case, the light metals will normally not require a special anti-corrosion layer. In practice, however, the composite material comprising the electrochemically base light metal alloys and the low-alloy steels commonly used in the construction of car bodies will cause corrosion problems due to the different electrochemical potentials of the materials.
For this reason, contact or joint regions between the different materials require considerable expenditure to protect them from contact corrosion. This holds true, for example, for vehicle bodies which are typically exposed to an ingress of corrosive aqueous media. In this regard, a typical measure in vehicle construction is seam sealing wherein a special plastic sealing is applied on the joint seam between the two materials.
When connecting the joints, use must frequently be made of bonding so as to prevent direct electrochemical contact between the different materials. This is described, for example, in DE 19939977 A1.
A further composite material which causes problems due to contact corrosion is a mixed construction of steel and copper. In such a construction, the Cu alloy, when compared to the steel, is the more precious component. Here the contact site must also be protected against the formation of a local element by use of special measures.
With regard to the demands on reliable and inexpensive corrosion protection, for example, in the regions of joints, the known techniques and methods for manufacturing vehicle body components or the basic structure of the vehicle body by utilizing mixed-construction technology are, now as before, unsatisfactory.